End-fire array microphone arrangements inside a vehicle

ABSTRACT

The present application discloses exemplary arrangements of an end-fire microphone array inside a vehicle and exemplary digital signal processors configured for the end-fire in-car microphone array. The exemplary digital signal processors may be configured in two modes, a phone call mode and an automatic speech recognition mode. In each mode, the exemplary digital signal processors are improved for enhanced SNR. Different end-fire microphone array arrangements are also disclosed.

FIELD OF THE INVENTION

The present disclosure relates generally to audio devices and morespecifically to optimal arrangements of microphones and improved signalprocessing inside a vehicle.

BACKGROUND OF THE INVENTION

Nowadays telephones are commonly installed inside a vehicle to allow thedriver to initial or receive a phone call without taking hands off thewheel. Such built-in telephones rely on microphones to pick up voicesignals in a high-noise background where there are multiple noisesources in a reverberant environment. This imposes high signal overnoise ratio enhancement (SNRE) performance requirements on the audiodevice used in the built-in telephones inside a vehicle.

In some cases, a driver may install their mobile phone on the dash boardto make or answer a phone call while keeping hands on the wheel. Whenthe driver initiates a call using voice command, the phone is activatedthrough voice recognition. In this voice recognition mode, themicrophone associated with the mobile phone must pick up the voicecommand amid the noises and the signal processor must separate the voicesignal from the background noises. When the driver engages in a phonecall without a headset, the microphone associated with the mobile phonemust cancel echoes that are inevitably generated in a reverberantenvironment inside a vehicle. In this phone call mode, the microphoneand the signal processor should be configured with noise reduction andecho cancellation functionalities.

Prior art audio systems are not ideally configured to provide aneffective hands-free audio application for use inside a vehicle. Thepresent application teaches various embodiments that are especiallysuitable to use in a relatively noisy and reverberant environment, suchas, the interior of a vehicle.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present disclosure to teach anaudio system that is suitable for use inside a vehicle.

In some embodiments, an exemplary audio system comprises an array of oneor more microphones in an end-fire configuration. The microphone arrayis located on a charging device. The exemplary audio system furthercomprises a dual-mode digital signal processor configured to operate inan automatic speech recognition mode and a phone call mode. In theexemplary audio system, each of the one or more microphones generates anaudio signal as an input to the dual-mode digital signal processor. Insome embodiments, the charging device may be a USB charging cable. Themicrophone array may be located on the head of the US charging cable.For example, the microphone array may be located on the same side of theUSB head or both sides of the USB head or a side-edge of the USB head.

In some embodiments of the exemplary audio system, the digital signalprocessor comprises a beamforming module configured to output twocardioid beams. In one embodiment, the beamforming module is an adaptivenoise cancellation (ANC) beamforming module and the ANC beamformingmodule generates a front-facing main beam and an omni-directionalreference beam. In one embodiment, the beamforming module is a voiceactivity detection (VAD) beamforming module. The VAD beamforming moduleis configured to generate a front facing beam and a back facing beam.

In some embodiments, the dual-mode digital signal processor comprises anadaptive noise cancellation module for cancelling environmental noise.In some embodiments, the digital signal processor is a dual-mode digitalprocessor that comprises a beamforming module and an adaptive noisecancellation module. The digital signal processor may further comprise avoice activity detection module for speech recognition, an echocancellation module for cancelling echo noise, and/or a double-talkdetector module for detecting voice signals from one or more speakersand for removing or separating the detected voice signals from the totalsignals collected by the end-fire microphone array.

In some embodiments of the exemplary audio system, the audio systemcomprises an array of one or more microphones in an end-fireconfiguration and a dual-mode digital signal processor. The microphonearray is located on an edge of a smartphone and is aligned along a lineperpendicular to the edge. Each microphone in the microphone arraygenerates an audio signal as an input to the dual-mode digital signalprocessor. The dual-mode digital signal processor is configured tooperate in an automatic speech recognition mode and a phone call mode.

In some embodiments, the dual-mode digital signal processor comprises abeamforming module configured to output two cardioid beams. In oneembodiment, the beamforming module generates a front-facing main beamand an omni-directional reference beam for adaptive noise cancellationpurposes. In another embodiment, the beamforming module generates afront-facing beam and a back-facing beam for voice activity detectionpurposes. In some embodiments, the dual-mode digital signal processorcomprises an adaptive noise cancellation module for cancellingenvironmental noises. In some embodiments, the dual-mode digital signalprocessor comprises an echo cancellation module for cancelling echo. Inone embodiment, the dual-mode digital signal processor may comprise abeamforming module, an adaptive noise cancellation module, and/or anecho cancellation module. In some embodiments, the dual-mode digitalprocessor further comprises a double-talk detector module for detectingvoice signals from one or more speakers and removing the detected voicesignals from the total signals collected by the end-fire microphonearray.

In some embodiments, an exemplary audio system comprises an array offour or more microphones. At least two microphones in the microphonearray are arranged at one end of a rear-view mirror in an end-fireconfiguration and at least two microphones in the microphone array arearranged at the other end of a rear-view mirror in an end-fireconfiguration. The exemplary audio system further comprises a dual-modedigital signal processor configured to operate in an automatic speechrecognition mode and a phone call mode. In the exemplary audio system,each of the one or more microphones generates an audio signal as aninput to the dual-mode digital signal processor. The dual-mode digitalsignal processor comprises a beamforming module configured to output afront-facing main beam and an omni-directional reference beam. In someembodiments, the dual-mode audio processor further comprises an adaptivenoise cancellation module for cancelling environmental noise. Thedual-mode audio processor may further comprise a voice activitydetection module for speech recognition, an echo cancellation module forcancelling echo, and/or a double-talk detector module for detectingvoice signals from one or more speakers and removing the detected voicesignals from the total signals collected by the end-fire microphonearray.

In some embodiments, an exemplary audio system comprises an array of oneor more microphones in an end-fire configuration and a dual-mode digitalsignal processor. The microphone array is located on an accessary deviceinstalled inside a vehicle and is arranged in a forward-facing directionof driver of the vehicle. Each microphone in the microphone arraygenerates an audio signal as an input to the dual-mode digital signalprocessor. The accessory device can be a phone holder, a dashboardcamera, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the present disclosure will become readilyapparent upon further review of the following specification anddrawings. In the drawings, like reference numerals designatecorresponding parts throughout the views. Moreover, components in thedrawings are not necessarily drawn to scale, the emphasis instead beingplaced upon clearly illustrating the principles of the presentdisclosure.

FIGS. 1A-1C show a first exemplary embodiment of an end-fire array ofmicrophones for use inside a vehicle.

FIG. 2 is a first exemplary embodiment of a digital signal processor foran end-fire in-car microphone array.

FIG. 3 is a second exemplary embodiment of a digital signal processorfor an end-fire in-car microphone array.

FIG. 4 is an illustration of beamforming patterns when an end-firein-car microphone array is in a phone call mode.

FIG. 5 is an illustration of beamforming patterns when an end-firein-car microphone array is in an automatic speech recognition mode.

FIG. 6 illustrates a second exemplary arrangement of an end-fire in-carmicrophone array.

FIG. 7 illustrates a third exemplary arrangement of an end-fire in-carmicrophone array.

FIG. 8 illustrates a fourth exemplary arrangement of an end-fire in-carmicrophone array.

FIG. 9 illustrates a fifth exemplary arrangement of an end-fire in-carmicrophone array.

DETAILED DESCRIPTION

Embodiments of the disclosure are described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the disclosure are shown. The various embodiments of the disclosuremay, however, be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein. Rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the scope of the disclosure to thoseskilled in the art.

In referring to FIGS. 1A-1C, an exemplary configuration of an end-firemicrophone array 100 is illustrated. As an example, the microphonearrays 100 in FIGS. 1A-1C are shown to comprise two microphones. In someembodiments, the microphone array can include more than two microphones.In certain configurations, the microphone array may include just onemicrophone. In FIGS. 1A-1C, the two microphones, 100 and 101, arelocated, respectively, on the front and back side of the head 150 of acharging cable, for example, a USB charging cable. FIG. 1A shows thefront side of the cable head 150 with the microphone 100. FIG. 1B showsthe back side of the cable head 150 with the microphone 101 aligned withthe microphone 100. FIG. 1C shows a side view of the cable head 150.

When the charging cable is plugged into a mobile phone operating in avehicle, the microphone array 100 along with its associated digitalsignal processor provides enhanced audio processing functionalities tothe mobile phone. FIG. 2 and FIG. 3 illustrate two exemplaryconfigurations of a digital signal processor (DSP).

In FIG. 2, the digital signal processor 200 is configured to provideoptimal audio processing functionalities when the microphone array 100is in a phone call mode. When in a phone call mode, the microphones, 204and 206, pick up the voice signals from the speaker 202 and the echo ofthe voice signals of the speaker 202, in addition to the voice signalsfrom the human being engaged in the phone call. The voice signals fromthe speaker 202 and the echo generated from those voice signals areenvironmental noises and should be removed from the voice signalscollected from the human being. In a reverberant environment such as theinterior of a car, the voice signals from the speaker 202 and the echobecome significant noise and should be removed from the true voicesignals.

In FIG. 2, the digital signal processor 200 includes a plurality ofmodules 212-232. The double talk detector module 212 is configured tosample audio signals that is fed into the speaker 202 and iscontemporaneous with the voice signals collected by the microphones, 204and 206, i.e., the so-called double-talk signals. When double talking isdetected, the double talk detector module 212 activates the echocancellation module 214 and 216. The echo cancellation modules 214 and216 are configured to subtract the audio signals of the speaker 202 fromthe microphone signals. By doing so, the audio signals broadcasted fromthe speaker 202 and the echo of such audio signals, both collected bythe microphones 204 and 206 as environment noises, are cancelled fromthe microphone signals, resulting in a clean signal that includessubstantially the voice signal of the human being engaged in the phonecall.

In the embodiment shown in FIG. 2, the digital signal processor 200 alsoincludes two beamforming modules: the beamforming module for activenoise cancelling (ANC) 220 and the beamforming module for voice activitydetection (VAD) 218. The ANC beamforming module 220 generates a frontfacing main beam and a omni reference beam that both are fed into thenoise cancellation module 222. The VAD beamforming module 218 generatesa front facing beam and a back-facing beam, both of which are fed intothe VAD module 224. Illustration of the different beams can be found inFIGS. 4 and 5. The signal output by the VAD module 224 is also inputinto the noise cancellation module 222, which is configured to producespeech signal based on the input signals from the ANC beamforming module220 and the VAD module 224.

For better quality, additional modules can be added after the noisecancellation module 222. For example, as shown in FIG. 2, the noisecancellation module 222 is a dual-channel adaptive noise cancellationmodule 222 and a single channel noise reduction module 226 may be addedto reduce the noise level further. A non-linear processing module 230that further improves the audio signal can also added in someembodiments. Both the single channel noise reduction module 226 and thenon-linear processing module 230 take input signals from a singlechannel VAD module 228 and 232 respectively to generate a clean speechsignal.

FIG. 3 illustrates an exemplary digital signal processor 300 forprocessing audio signals when in an automatic speech recognition (ASR)mode. In the ASR mode, the digital signal processor 300 is configured todetect a voice command when there is not an active phone call. In suchcase, there is no voice signal being fed into the speaker and it is notnecessary to perform echo cancellation. In the digital signal processor300, the signals collected by the two microphones, the front microphone304 and the back microphone 306, are fed into the ANC beamforming module312 and the VAD beamforming module 314. The ANC beamforming module 312generates a front-facing main beam and an omni reference beam. Bothbeams are input into a dual-channel adaptive noise cancellation module316, after which a single channel noise reduction module 320 and anon-linear processing module 324, both coupled with a single channel VADmodule, 322 and 326 respectively, are employed to produce a clean speechsignal. The VAD beamforming module 314 generates a front-facing beam anda back-facing beam that are fed into a directional voice activitydetection module 318. The output from the directional voice activitydetection module 318 indicates the direction of the voice activity andis input into the dual channel adaptive noise cancellation module 316.

FIG. 4 and FIG. 5. illustrate the beam forming mechanism used in the ANCbeamforming module and the VAD beamforming module. In FIG. 4, the twobeams, 402 and 404, generated by the ANC beamforming module 312 areshown. The beam 402 is a front facing cardioid beam, which has a null inthe back-facing direction and a maximum facing forward. The beam 402comprises both desired voice signal and noise. It is the main beam. Thesecond beam, 404, is an omni beam that is substantially devoid of voicesignal. The beam 404 is a reference beam that represents the backgroundnoises and is used to cancel the noises in the main beam 402. Bothbeams, 402, and 404, are fed into the noise cancellation module 316 fornoise reduction and cancellation.

In FIG. 5, the VAD beamforming module 314 generates a front facingcardioid beam 502 and a back facing cardioid beam 504. The front facingcardioid beam 502 comprises a maximum at the front side of the beam anda null at the back side of the beam. The back facing cardioid beam 504comprises a null at the front side of the beam and a maximum at the backside of the beam. Both beams, 502 and 504, are fed into the directionalvoice activity detection module 318 for processing. As a skilled personin the art would know, the directional voice activity detection module318 may comprises various signal processing components such asconverters, filters, delay elements, adder, comparator, etc. In someembodiments, the directional voice activity detection module 318 isconfigured to generate a narrow spotlight beam pattern that isindicative of the direction of the voice activity.

In the above description, a microphone array of two microphones is usedas an example for illustration purposes. However, the embodiments arenot so limited. In alternate embodiments, two or more microphones can beused to generate beams. Generally, the microphones in a microphone arrayare disposed proximally adjacent to each other. For certain applicationsthat involve human interface, the separating distance between twoadjacent microphones may be in the range as small as 0.2 cm to lcm.Other applications, e.g., semiconductor acoustic devices, the separatingdistance may be in the order of microns or sub-microns. While thedistance of two adjacent microphones is constraint by the likelihood ofcross interference between the elements, their relative positions, e.g.,whether the microphones face the expected originating direction of adesired voice signal in parallel or in series, are not as important astheir respective beam patterns.

In the above description, the term “microphone” is used in describingvarious embodiments. It is noted that the principles and the theoriesdisclosed herein are applicable to embodiments in which different typesof acoustic devices other than microphones may be used in place ofmicrophones.

FIGS. 6-9 illustrates four more exemplary arrangements of an array ofacoustic devices or microphones.

FIG. 6 shows a bottom edge of a smart phone 600. On the bottom edge ofthe smart phone are a 3.5 mm headphone jack 606, a cable connector 608,e.g., USB cable, and an array of built-in speakers 610. An array ofmicrophones comprising a front microphone 602 (close to the front sideof the smart phone) and a back microphone 604 (close to the back side ofthe smart phone) are disposed on the bottom edge of the smart phone inbetween the headphone jack 606 and the cable connector 608. Themicrophones 602 and 604 face the expected originating direction, i.e.,the user who is speaking into the front side of the smart phone, inseries.

In FIG. 7, a rearview mirror 700 used inside a vehicle is shown ascomprising two microphone arrays. Each microphone array, 702 or 704,comprises two microphones, 706 and 708, and disposed on one end of andat the lower edge of the rearview mirror 700. The microphones 706 and708 face the expected originating direction, a driver sitting in frontof the rearview mirror 700, in parallel.

In FIG. 8, a phone holder 800 is shown as holding a smartphone. Thephone holder 800 can be used inside a vehicle to allow the driver tomake or receive phone calls hands-free. In this embodiment, themicrophones 802 and 804 are disposed on the phone holder, not on thesmartphone. The microphones 802 and 804 are arranged to face theexpected originating direction, i.e., the driver facing the front faceof the smartphone, in series.

FIG. 9 illustrates a microphone array 800 arranged on a dashboard camerainstalled inside a car, e.g., on the dashboard or windshield. Thedashboard camera is in front of the driver of the car. The microphonearray 800 comprises two microphones, 802 and 804. The microphone array800 is placed at the lower left corner of the dashboard camera and themicrophones, 802 and 804, are arranged to face the expected originatingdirection, i.e., the driver facing the dashboard, in series. In someembodiments, there may be two microphone arrays, one on each lowercorner of the dashboard camera.

Although the disclosure is illustrated and described herein withreference to specific embodiments, the disclosure is not intended to belimited to the details shown. Rather, various modifications may be madein the details within the scope and range of equivalents of the claimsand without departing from the disclosure.

What is claimed is:
 1. An audio system, comprising: an array of one ormore microphones in an end-fire configuration, wherein the microphonearray is located on a charging device; and a dual-mode digital signalprocessor configured to operate in an automatic speech recognition modeand a phone call mode; wherein each of the one or more microphonesgenerates an audio signal as an input to the dual-mode digital signalprocessor.
 2. The audio system of claim 1, wherein the charging deviceis a USB charging cable and the array of microphones is located on thehead of the USB charging cable.
 3. The audio system of claim 2, whereinthe microphone array is located on the same side of the head.
 4. Theaudio system of claim 2, wherein the array of microphones is arranged tobe located on different sides of the head.
 5. The audio system of claim4, wherein the different sides of the head are side-edges of the head ofthe USB charging cable.
 6. The audio system of claim 1, wherein thedual-mode digital signal processor comprises a beamforming module, andwherein the beamforming module is configured to output two cardioidbeams.
 7. The audio system of claim 6, wherein one of the two cardioidbeams is a front facing main beam and one of the two cardioid beams isan omni reference beam.
 8. The audio system of claim 6, wherein one ofthe two cardioid beams is a front facing main beam and one of the twocardioid beams is a back facing beam.
 9. The audio system of claim 6,wherein the dual-mode audio processor further comprises an adaptivenoise cancellation module for cancelling environmental noise.
 10. Theaudio system of claim 6, wherein the dual-mode audio processor furthercomprises a voice activity detection module for speech recognition. 11.The audio system of claim 6, wherein the dual-mode audio processorfurther comprises an echo cancellation module for cancelling echo. 12.The audio system of claim 6, wherein the dual-mode audio processorcomprises a double-talk detector module for detecting voice signals fromone or more speakers and removing the detected voice signals from voicesignals collected by the end-fire microphone array.
 13. An audio system,comprising: an array of one or more microphones in an end-fireconfiguration, wherein the microphone array is located on an edge of asmartphone and wherein the microphone array is aligned along a lineperpendicular to the edge; and a dual-mode digital signal processorconfigured to operate in an automatic speech recognition mode and aphone call mode; wherein each of the one or more microphones generatesan audio signal as an input to the dual-mode digital signal processor.14. The audio system of claim 13, wherein the dual-mode digital signalprocessor comprises a beamforming module, and wherein the beamformingmodule is configured to output two cardioid beams.
 15. The audio systemof claim 14, wherein one of the two cardioid beams is a front facingmain beam and one of the two cardioid beams is an omni reference beam.16. The audio system of claim 14, wherein one of the two cardioid beamsis a front facing main beam and one of the two cardioid beams is a backfacing beam.
 17. The audio system of claim 13, wherein the dual-modeaudio processor further comprises an adaptive noise cancellation modulefor cancelling environmental noise.
 18. The audio system of claim 13,wherein the dual-mode audio processor further comprises a voice activitydetection module for speech recognition.
 19. The audio system of claim13, wherein the dual-mode audio processor further comprises an echocancellation module for cancelling echo.
 20. The audio system of claim13, wherein the dual-mode audio processor comprises a double-talkdetector module for detecting voice signals from one or more speakersand removing the detected voice signals from voice signals collected bythe end-fire microphone array.
 21. An audio system, comprising: an arrayof four or more microphones, wherein at least two microphones in themicrophone array are arranged at one end of a rear-view mirror in anend-fire configuration and wherein at least two microphones in themicrophone array are arranged at the other end of a rear-view mirror inan end-fire configuration; and a dual-mode digital signal processorconfigured to operate in an automatic speech recognition mode and aphone call mode; wherein each of the one or more microphones generatesan audio signal as an input to the dual-mode digital signal processor.22. The audio system of claim 21, wherein the dual-mode digital signalprocessor comprises a beamforming module, and wherein the beamformingmodule is configured to output two cardioid beams.
 23. The audio systemof claim 21, wherein the dual-mode audio processor further comprises anadaptive noise cancellation module for cancelling environmental noise.24. The audio system of claim 21, wherein the dual-mode audio processorfurther comprises a voice activity detection module for speechrecognition.
 25. The audio system of claim 21, wherein the dual-modeaudio processor further comprises an echo cancellation module forcancelling echo.
 26. The audio system of claim 21, wherein the dual-modeaudio processor comprises a double-talk detector module for detectingvoice signals from one or more speakers and removing the detected voicesignals from voice signals collected by the end-fire microphone array.27. An audio system, comprising: an array of one or more microphones inan end-fire configuration, wherein the microphone array is located on anaccessory device installed inside a vehicle; and a dual-mode digitalsignal processor configured to operate in an automatic speechrecognition mode and a phone call mode; wherein the one or moremicrophones are arranged in a forward-facing direction of the driver ofthe vehicle; and wherein each of the one or more microphones generatesan audio signal as an input to the dual-mode digital signal processor.28. The audio system of claim 27, wherein the accessory device is aphone holder.
 29. The audio system of claim 27, wherein the accessorydevice is a dashboard camera.